Switch

WAN is a network that covers a broad geographic area, which often uses service providers’ (SP) transmission facilities and operates on Physical Layer#, Data Link Layer# and Network Layer# to connect several #Local-Area Network (LAN). Several network devices could operate within WAN such as Switch# (at data link layer) and Router#.

VLAN is a logical grouping of devices that breaks the physical boundaries among them. This means that the devices connected to different #Switch or in different network can still able to be treated as a single group. It abstracts the network grouping and allows hosts to be treated as a single group based on their business role.

We can apply access rules and provision services to the users of same or similar responsibilities without the need to change the topology of the network or changing the IP Address. Furthermore, VLAN can also create their own Broadcast Domain# without the help from Network Layer Network Device (modern #Switch and #Router). Basically, we could assign the hosts in a subnet# to be in the same VLAN. By using VLAN, we could have different broadcast domains even in a single switch so that broadcast flooding affects only those in the same grouping. If a link needs to handle more than one VLAN, #VLAN Trunking will be used.

Note: These two standards are incompatible to each other. If two Switch# support different standard and only that standard, then it is not possible to establish a trunk link between them.

In a typical Local-Area Network (LAN)# network, it is designed as a Hierarchical Network# involving multiple Switches# with three layers: core layer, distribution layer, access layer. Access layer consists of end devices, and defines a basic configuration and constraint on them on network connection. Distribution layer is where we will define routing policies, Virtual LAN (VLAN)#, access control, broadcast domains, and access layer traffic aggregation or funnelling. Core layer should be capable of handling large amounts of traffic with high performance, this means that it needs to be highly available and redundant. For cost saving, we can collapse or combine distribution layer and core layer into one single layer.

When considering a Switch#, we should inspect the traffic flow analysis (bandwidth usage and data analysis), user community analysis (impact of the user groups on network performance), data sources and data servers analysis (their locations and traffic for client-server and server-server), and network topology (port numbers, aggregated ports, redundant paths, etc.). Furthermore, we need to inquire the ability of the switch such as port density, forwarding rate, link aggregation ability, Power over Ethernet (PoE) ability, and Layer 3 functionality (using multilayer switch). Typically, lower performing switch should be in access layer# whereas higher performing one should be in distribution and core layers.

Store-And-Forward Switching is a kind of #switching mode that waits to receive the entire frame before forwarding. It will first read such a frame, then pass it to cyclic redundancy check (CRC). If the CRC is bad, the frame will be simply discarded, which could causes some latency but minimises errors at the same time.

Stackable #Switches are interconnected with a backplane cable that provides high-bandwidth throughput between switches using technologies such as Cisco StackWise. They will operate as a single entity, which is quite desirable for building a highly available network.

STP is a #202206131651 protocol designed to run on 202207051851# and 202207051907# in order to prevent #202207081644 inside the network. It has been standardised by the Institute of Electrical and Electronic Engineers (IEEE) with 802.1d.

Router consists of two types of interfaces: LAN interfaces and WAN interfaces. LAN interfaces could be used to connect Router to the LAN which is typically connected with an RJ-45 jack (Unshielded Twisted Pair Cable (UTP)). For connecting Router to Switch, we use a Straight-Through Cable. In the case of Router to Router, we use a Crossover Cable. For PC to Router, we will use Roll-Over Cable. LAN interface could serve Ethernet# and Fast Ethernet.

The process of forwarding the packet from its received port to the outgoing port is called switching. Despite the naming, Router will immediately drop the packet when it can’t figure the destination in its routing table maintained by itself. Otherwise, it will simply modify the destination Media Access Control Address (MAC) (the next-hop, can be another Router or the final destination) in the packet without touching the IP Address which defines the final destination. Though the primary forwarding decision will be based on the Routing Table# or routing information, assuming there is a mapping of logical address to its interface or port. If there is no path defined in the routing table to where the packet should be forwarded to, Router will redirect it to a default route if set (usually 0.0.0.0 in IPv4 Address and ::/0 in IPv6 Address), or simply discards it and sends Internet Control Message Protocol (ICMP)# Unreachable message to the source. Additionally, we can divide a physical interface into at most 65,535 logical interfaces using the command interface {interface-name} {interface}.{subinterface}. This is particularly useful in Virtual LAN (VLAN) routing.

Network Loop could happen when there is a redundancy within the network, especially in 202207051851# and 202207051907# network. The packet could be trapped in a circle where they will travel endlessly around the same path. As more and more packets get involved in the loop, the network will inevitably come to a halt as no more bandwidth is available to the hosts due to broadcast-storms (infinite flooding of frames originally for broadcasting), multiple copies of frames (most protocols can’t handle duplicated transmissions), and 202206151451 address table instability (receiving the same frame on different ports).

There are three primary equipment types within a MPLS network: **customer premises equipment (CPE), provider edge (PE), and provider routers (P). CPE will be on the customer site, and all the traffic leaving the local site is routed through it. PE, could be a high-end switch or router, is at the entry point of the service provider’s network. P locates in the core of the network, which will be responsible on forwarding packets based on the labelling.

Modular #Switch could come in different sized chassis that allow additional modular line cards (more ports) to be installed on it.

Link/Carrier Availability usually refers to the design practice that home multiple servers, establish multiple link connections between Switch and Router, and/or subscriptions to several service providers.

ISR is a kind of #Router that combine the functionalities of Switch#, wireless access point and router. It is widely adopted for the home Local-Area Network (LAN).

The address could be assigned via static method or dynamic method#. For general case, devices that don’t move too much such as servers, Router# and Switch# are assigned with static IP address. Mobile devices like laptop and smartphone should be using dynamic method to get the IP address instead.

Networks could divide Router or Switch into several logical grouping#. In turn, this simplifies the routing updates as they will be confined within the grouping, and drastically reduces the traffic overhead. Notice its similarity to VLAN.

Virtual circuit# is basically a logical connection between two data terminal equipment (DTE) devices, such as terminals, PCs, routers and bridges, across a Frame Relay packet-switched network which can be uniquely identified by data-link connection identifier (DLCI) at the network endpoints. Since it is logical, within a single physical circuit there can exist multiple virtual circuits. Within this virtual circuit, there could be multiple data communications equipments (DCE), usually a Switch#, which provides clocking and switching services in a network.

Fragment-Free Switching is a kind of #202207051907 which forwards the frame after reading the first 64 bytes of it. It is basically a modified 202207061210.

Fixed Configuration #Switch is fixed in their configuration which means that the default features or options could not be altered by the user.

Using Switch# can greatly improve the network throughput (bandwidth) by configure the port connected to the Ethernet as full duplex (two-way communications, simultaneously receive incoming traffic and transmit traffic).

DTP is a Cisco proprietary Point-to-Point Protocol# used between Switches# for automatic trunk# negotiation. Depending on modes set on both end, DTP can decide whether the link should be trunk or non-trunk. The following table shows the outcome for the link for different composition of opposite ports.

Cut-Through Switching, aka fast-forward switching, is a kind of #switching mode that immediately forwards the frame received after the check on destination 202206151451#. Latency is not a problem, but in this mode, frames errors will be easily transmitted to other network segments.

CWDM uses wavelength-specific pairs of Gigabit Interface Converters (GBIC) connected to a Switch# pair in order to #multiplex up to 8 #Fibre-Optic Cable signals onto a single fibre. Each GBIC pair is tuned to a specific frequency that allows the switch to add (mux) or pluck out (demux) a single beam of light (data stream). However, CWDM is unable to be amplified, which limited its maximum distance to 80 km for point-to-point or a ring circumference of 30 km.

To configure #Virtual LAN (VLAN) with Switch#, there is a need to set up an IP Address, subnet mask, and default gateway (router to direct switch management traffic for remote access such as Telnet and Secure Shell (SSH)) in a switch. The configuration could be done in IOS# with the command vlan {number} in Interface Configuration Mode follows by the IP address assigned to the VLAN. We can attach a name to a VLAN by simply running the command name {vlan-name} right after vlan {number} command in Global Configuration Mode. Define the VLAN membership mode for the assigned interface (port) as access (see Dynamic Trunking Protocol (DTP)# for other possible modes) with switchport mode {mode} and assign VLAN to it by switchport access vlan {number} in the Interface Configuration Mode.

Cisco IOS is a collection of network operating systems used on Cisco Network Devices#, usually stored at the flash of the device or TFTP server. It can be used from input and output devices. It also provides the mean for memory management, process management, file systems management, security management, hardware management, network interface configuration, and enabling routing# and switching# functions.

Circuit Switching is a #Wide Area Network (WAN) technology that allows private connection from multiple sites to a single carrier’s switched network in order to communicate with each other. This can be done by using a physical switch#. It is originated from telephone network.

Broadcast Domain is a network segment where a device can receive all broadcast messages from the members of the segment. It is usually segmented by Network Layer# Network Device# (modern #Switch and #Router).

ATM is a Wide Area Network (WAN) technology that support both #Packet Switching and #Circuit Switching functionalities. It operates at #Data Link Layer. The basic components in an ATM network are ATM switches#, which is responsible for moving cells through the network, and ATM endpoints, such as workstations, Router, data service units (DSU) etc.